Air conditioner

ABSTRACT

An air conditioner includes an outdoor unit including a compressor, an outdoor heat exchanger, and a switching device, an indoor unit including a first heat exchanger and a throttle regulator, a discharge pipe connected to a discharge side of the compressor, a low-pressure suction pipe connected to a low-pressure suction side of the compressor, a first piping connecting the discharge pipe, the outdoor heat exchanger, the throttle regulator, and the first heat exchanger in sequence, a second piping connecting the first heat exchanger and the low-pressure suction pipe, an economizer arranged at the first piping between the outdoor heat exchanger and the throttle device, and first and second refrigerant flow paths arranged in the economizer. Refrigerant flow directions in the first and second refrigerant flow paths are opposite to each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Chinese Application No. 201911034323.1 filed to the Chinese Patent Office on Oct. 28, 2019 and entitled “AIR CONDITIONER,” and Chinese Patent Application No. 201921830849.6 filed to the Chinese Patent Office on Oct. 28, 2019 and entitled “AIR CONDITIONER,” the entire contents of both of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to the technical field of air conditioning, and in particular to an air conditioner.

BACKGROUND

With the increasing improvement of people's living standards and the demand for energy saving, the enhanced vapor injection refrigerant system is more and more widely used, especially in applications of coal-to-electricity conversion and multi-split air conditioners in northern China. In addition, as for multi-split air conditioner systems or other refrigerant systems, due to the application of long connection pipes and the existence of throttle devices on the indoor machine side, many systems are provided with secondary subcoolers to reduce pipeline pressure loss and indoor machine throttling noise. When both enhanced vapor injection and secondary subcooling are required on a refrigerant system application, an economizer may be shared. However, due to the opposite flow directions of cooling and heating refrigerants, the economizer is bound to perform downstream heat exchange in one of the directions, which results in a small temperature difference for heat exchange and a low heat exchange efficiency.

SUMMARY

A main objective of the present disclosure is to provide an air conditioner which aims to enable the air conditioner to have a high heating capacity in low-temperature environments while having a thermostatic dehumidification function.

In order to achieve the above purpose, the air conditioner provided in the present disclosure includes an outdoor unit and an indoor unit, where the outdoor unit includes an enhanced compression mechanism and an outdoor heat exchanger, and the indoor unit includes a first heat exchanger and a first throttle regulator;

the air conditioner further includes: a discharge pipe connected to a discharge side of the compression mechanism, a low-pressure suction pipe connected to a low-pressure suction side of the compression mechanism, a first piping connecting the discharge pipe, the outdoor heat exchanger, the first throttle regulator, and the first heat exchanger in sequence, and a second piping connecting the first heat exchanger and the low-pressure suction pipe, thus forming a refrigerant circuit;

the outdoor unit further includes a first switching device, the first switching device being capable of switching between a first switching state of the first switching device and a second switching state of the first switching device, where in the first switching state the first switching device causes the first piping to communicate with the suction pipe and the second piping to communicate with the discharge pipe, and in the second switching state the first switching device causes the first piping to communicate with the discharge pipe and the second piping to communicate with the suction pipe;

the air conditioner further includes an economizer, where the economizer is provided at the first piping between the outdoor heat exchanger and the first throttle device; a first refrigerant flow path and a second refrigerant flow path are provided in the economizer, the first refrigerant flow path being connected in the first piping through a refrigerant bridge; and one end of the second refrigerant flow path communicates with the first piping through a liquid pickup pipe and the other end communicates with both a medium-pressure suction port of the compressor and the suction pipe through a return pipe, so that refrigerant flow directions in the first refrigerant flow path and the second refrigerant flow path are opposite to each other.

In some embodiments, the refrigerant bridge has a first port, a second port, and a refrigerant passage that causes the first port to communicate with the second port, and the refrigerant bridge is connected in the first piping through the first port and the second port.

In some embodiments, the refrigerant bridge has a third port and a fourth port, and the two ends of the first refrigerant flow path are connected to the third port and the fourth port, respectively;

the first port communicates with the third port through a first bridge section, the first bridge section allowing unidirectional fluid flow from the first port to the third port;

the third port communicates with the second port through a second bridge section, the second bridge section allowing unidirectional fluid flow from the second port to the third port;

the second port communicates with the fourth port through a third bridge section, the third bridge section allowing unidirectional fluid flow from the fourth port to the second port; and

the fourth port communicates with the first port through a fourth bridge section, the fourth bridge section allowing unidirectional fluid flow from the fourth port to the first port.

In some embodiments, the refrigerant bridge has a third port and a fourth port, and the two ends of the first refrigerant flow path are connected to the third port and the fourth port, respectively;

the first port communicates with the third port through a first bridge section, the first bridge section allowing unidirectional fluid flow from the third port to the first port;

the third port communicates with the second port through a second bridge section, the second bridge section allowing unidirectional fluid flow from the third port to the second port;

the second port communicates with the fourth port through a third bridge section, the third bridge section allowing unidirectional fluid flow from the second port to the fourth port;

the fourth port communicates with the first port through a fourth bridge section, the fourth bridge section allowing unidirectional fluid flow from the first port to the fourth port.

In some embodiments, the first bridge section, the second bridge section, the third bridge section, and the fourth bridge section are each provided with a one-way valve.

In some embodiments, the liquid pickup pipe is provided with a liquid pickup throttle valve.

In some embodiments, the return pipe includes a return pipe body, a first communication pipe, and a second communication pipe;

one end of the first communication pipe communicates with the return pipe body and the other end communicates with the medium-pressure suction port of the compressor; the return pipe body or the first communication pipe is provided with a first control valve;

one end of the second communication pipe communicates with the return pipe body and the other end communicates with the suction pipe, and the second communication pipe is provided with a second control valve.

In some embodiments, an inflow end of the liquid pickup pipe communicates with the first piping between the economizer and the outdoor side heat exchanger, or

an inflow end of the liquid pickup pipe communicates with the first piping between the economizer and the first indoor throttle regulator.

In some embodiments, an inflow end of the liquid pickup pipe has a liquid pickup port at a junction with the first piping, the liquid pickup port being located below the first piping around the liquid pickup port.

In some embodiments, the air conditioner further includes a liquid pickup structure having a liquid pickup chamber and a first refrigerant port, a second refrigerant port, and a liquid pickup port that communicate with the liquid pickup chamber, the liquid pickup port being located below the first refrigerant port and the second refrigerant port.

In some embodiments, the air conditioner further includes a second heat exchanger, a second throttle regulator, a third piping, and a branch pipe branching off from the discharge pipe, the third piping connecting a first intersection point of the first piping, the second throttle regulator, the second heat exchanger, and the branch pipe in sequence, where the first intersection point is located between the first throttle regulator and the outdoor heat exchanger, and the economizer is located at the first piping between the first intersection point and the outdoor heat exchanger.

In some embodiments, the third piping communicates with the branch pipe, and a third control valve is provided at the branch pipe to control the opening and closing of the branch pipe; and the third piping communicates with the low-pressure suction pipe or with the second piping through a coupling pipe, and a fourth control valve is provided at the coupling pipe to control the opening and closing of the coupling pipe.

In some embodiments, the air conditioner further includes a second switching device, the second switching device being capable of switching between a third switching state and a fourth switching state of the second switching device,

in the third switching state, the second switching device causes the third piping to communicate with the branch pipe,

in the fourth switching state, the second switching device causes the third piping to communicate with the suction pipe.

In some embodiments, the air conditioner further includes an outdoor side throttle regulator, the outdoor side throttle regulator being located at the first piping between the economizer and the outdoor side heat exchanger.

In some embodiments, the air conditioner further includes: a first connection pipe branching off from a second intersection point of the first piping and a second connection pipe branching off from the second piping, the second intersection point being located between the first throttle regulator and the outdoor heat exchanger, and the air conditioner further includes multiple indoor units, the multiple indoor units being connected in parallel to the first connection pipe and the second connection pipe.

In some embodiments, the economizer includes a plate heat exchanger or a double-pipe heat exchanger having a first end and a second end provided opposite to each other, where the first refrigerant flow path enters through the first end and exits through the second end and the second refrigerant flow path enters through the second end and exits through the first end;

or the first refrigerant flow path enters through the second end and exits through the first end and the second refrigerant flow path enters through the first end and exits through the second end.

In the technical scheme of the present disclosure, by connecting the refrigerant inflow end of the first refrigerant flow path of the economizer to the refrigerant bridge and setting the flow direction of the second refrigerant flow path, the refrigerant flow directions in the first refrigerant flow path and the second refrigerant flow path are always opposite to each other (whether in the heating mode where the refrigerant flows from the indoor heat exchanger to the outdoor heat exchanger, or in the cooling mode where the refrigerant flows from the outdoor heat exchanger to the indoor heat exchanger). In this way, the temperature difference between refrigerants in the first refrigerant flow path and the second refrigerant flow path is adequately maintained, so that the heat exchange effect between the first refrigerant flow path and the second refrigerant flow path can be ensured, which is conducive to ensuring the air replenishment effect of the economizer on the compressor in the heating mode, thus ensuring the heating capacity of the air conditioner in low-temperature environments; and which, at the same time, is conducive to ensuring the liquefaction effect (exhaust effect) of the economizer on the refrigerant in the cooling mode, ensuring that the refrigerant entering the indoor throttle device is in the liquid state, thus eliminating the abnormal sound generated in the indoor throttling process.

BRIEF DESCRIPTION OF DRAWINGS

In order to illustrate the embodiments of the present disclosure or technical schemes in the related art, the drawings used in description of the embodiments or the related art will be briefly described below, and obviously, the drawings in the following description are provided as merely some embodiments of the present disclosure, and for those of ordinary skill in the art, other drawings can be derived on the basis of the structures shown in these drawings without any inventive effort.

FIG. 1 is a schematic diagram of the structure of an embodiment of an air conditioner according to the present disclosure;

FIG. 2 is a schematic diagram of the structure of another embodiment of an air conditioner according to the present disclosure;

FIG. 3 is a schematic diagram of the internal structure of an embodiment in the heating mode at A in FIG. 2;

FIG. 4 is a schematic diagram of the internal structure of an embodiment in the cooling mode at A in FIG. 2;

FIG. 5 is a schematic diagram of the structure of another embodiment in the heating mode at A in FIG. 2;

FIG. 6 is a schematic diagram of the structure of another embodiment in the cooling mode at A in FIG. 2;

FIG. 7 is a partial enlarged view of an embodiment of a junction of a liquid pickup pipe with a first piping in an air conditioner according to the present disclosure;

FIG. 8 is a partial enlarged view of another embodiment of a junction of a liquid pickup pipe with a first piping in an air conditioner according to the present disclosure;

FIG. 9 is a partial enlarged view of yet another embodiment of a junction of a liquid pickup pipe with a first piping in an air conditioner according to the present disclosure; and

FIG. 10 is a partial enlarged view of yet another embodiment of a junction of a liquid pickup pipe with a first piping in an air conditioner according to the present disclosure.

DESCRIPTION OF REFERENCE NUMERALS

Reference Reference numeral Name numeral Name 100 Outdoor unit 110 Compressor 111 Discharge pipe 112 Branch pipe 113 Low-pressure suction 114 Coupling pipe pipe 120 Gas-liquid separator 131 First switching device 132 Second switching 133 First control valve device 134 First liquid pickup 140 First piping point 141 Outdoor side heat 142 Outdoor side throttle exchanger regulator 143 Economizer 144 Liquid pickup throttle valve 143a First refrigerant flow 143b Second refrigerant path flow path 145 Liquid pickup pipe 146 return pipe 147 Second communication 148 First communication pipe pipe 149 Second control valve 150 Second piping 160 Third piping 135 Second liquid pickup point 200 Indoor unit 210 Second heat exchanger 220 First heat exchanger 230 Second throttle regulator 240 First throttle regulator 250 Second connection pipe 260 First connection pipe 211 First intersection point 212 Second intersection point P Exhaust port M Medium-pressure suction S Low-pressure suction port port 310 Third control valve 320 Fourth control valve 510 First end 520 Second end 600 Refrigerant bridge 610 First port 620 Second port 630 Third port 640 Fourth port 650 First bridge section 660 Second bridge section 670 Third bridge section 680 Fourth bridge section Q First junction 800 Liquid pickup structure 810 Liquid pickup chamber 820 Second refrigerant port 830 First refrigerant port 840 Liquid pickup port 690 One-way valve

The achievement of the purpose, functional features and advantages of the present disclosure will be further illustrated in conjunction with the embodiments and with reference to the accompanying drawings.

DETAILED DESCRIPTION

The technical schemes in the embodiments of the present disclosure are described in the following with reference to the accompanying drawings in the embodiments of the present disclosure. It is obvious that the described embodiments are only some of the embodiments of the present disclosure instead of all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present disclosure without inventive effort are within the scope of the present disclosure.

It should be noted that all directional indications (such as up, down, left, right, front, back, . . . ) in the embodiments of the present disclosure are used only to explain the relative position relationship, movement situation, etc., among the components in a particular attitude (as shown in the attached figures), and if that particular attitude is changed, the directional indications change accordingly.

The following illustration will focus on the specific structure of the air conditioner.

Referring to FIGS. 1 to 4, the entire pipeline structure and component configuration of the air conditioner will first be introduced. In an embodiment of the present disclosure, the air conditioner includes an outdoor unit 100 and an indoor unit 200, where the outdoor unit 100 includes a compressor 110 and an outdoor side heat exchanger 141, and the indoor unit 200 includes a first heat exchanger 220 and a first throttle regulator 240;

the air conditioner further includes: a discharge pipe 111 connected to a discharge side of the compressor 110, a low-pressure suction pipe 113 connected to a low-pressure suction side of the compressor 110, a first piping 140 connecting the discharge pipe 111, the outdoor side heat exchanger 141, the first throttle regulator 240, and the first heat exchanger 220 in sequence, and a second piping 150 connecting the first heat exchanger 220 and the low-pressure suction pipe 113, thus forming a refrigerant circuit;

the outdoor unit 100 further includes a first switching device 131, the first switching device 131 being capable of switching between a first switching state of the first switching device 131 and a second switching state of the first switching device 131, where

in the first switching state the first switching device 131 causes the first piping 140 to communicate with the suction pipe and the second piping 150 to communicate with the discharge pipe 111, and in the second switching state the first switching device 131 causes the first piping 140 to communicate with the discharge pipe 111 and the second piping 150 to communicate with the suction pipe.

By the setting of the first switching device 131, in the first switching state the air conditioner is in the heating state, i.e., the first heat exchanger 220 is in the heating operation. In the second switching state, the air conditioner is in the cooling state. The first switching device 131 may be a four-way valve.

The air conditioner further includes an economizer 143, where the economizer 143 is provided at the first piping 140 between the outdoor side heat exchanger 141 and the first throttle device; a first refrigerant flow path 143 a and a second refrigerant flow path 143 b are provided in the economizer 143, the first refrigerant flow path 143 a being connected in the first piping 140 through a refrigerant bridge 600; and one end of the second refrigerant flow path 143 b communicates with the first piping 140 through a liquid pickup pipe 145 and the other end communicates with both a medium-pressure suction port of the compressor 110 and the suction pipe through a return pipe 146, so that refrigerant flow directions in the first refrigerant flow path 143 a and the second refrigerant flow path 143 b are opposite to each other.

Regarding the operation of the economizer 143, in the heating mode, the first switching device 131 is in the first state, in which case the discharge pipe 111 communicates with the second piping 150, so that the high-temperature and high-pressure refrigerant passes through the discharge pipe 111 and the second piping 150 and then enters the first heat exchanger 220 for heating, and then flows into the refrigerant bridge 600 through the first piping 140, and after being subject to the action of the refrigerant bridge 600, flows into the first refrigerant flow path 143 a of the economizer 143, and flows back to the first piping 140 after passing through the first refrigerant flow path 143 a, and passes through the outdoor throttle valve and the outdoor side heat exchanger 141, and then flows back to the compressor 110 through the suction pipe from the low-pressure suction port. The second refrigerant flow path 143 b of the economizer 143, after liquid pickup and passing through the plate heat exchanger to exchange heat with the first refrigerant flow path 143 a, flows through the return pipe 146 back to the medium-pressure suction pipe of the compressor 110. At the same time, the communication between the return pipe 146 and the suction pipe is cut off, so as to replenish air to the compressor 110, thus improving the heating capacity of the compressor 110 in low-temperature environments;

In the cooling mode, the first switching device 131 is in the second state, in which case the discharge pipe 111 communicates with the first piping 140, and the high-temperature and high-pressure refrigerant passes through the discharge pipe 111 and the first piping 140, enters the outdoor side heat exchanger 141, then passes through the outdoor side heat exchanger 141 and then the outdoor throttle valve, and then enters the first refrigerant flow path 143 a of the economizer 143 through the refrigerant bridge 600, and the first refrigerant flow path 143 a passes through the plate heat exchanger and then flows back to the first piping 140, and then along the first piping 140 and through the first indoor throttle device, enters the first heat exchanger 220 for cooling; the inflow end of the second refrigerant fluid communicates with the first piping 140, and the refrigerant passes through the plate heat exchanger to exchange heat with the refrigerant in the first refrigerant flow path 143 a (to perform heat exchange through the plate heat exchanger), and then flows through the return pipe 146 and the suction pipe back to the low-pressure suction port of the compressor 110, so that the refrigerant entering the room through the economizer 143 and the first piping 140 is in the liquid state, thus avoiding the harsh and abnormal sound generated by the indoor throttle devices during throttling process.

The economizer 143 includes a plate heat exchanger or a double-pipe heat exchanger having a first end 510 and a second end 520 provided opposite to each other, where the first refrigerant flow path 143 a enters through the first end 510 and exits through the second end 520 and the second refrigerant flow path 143 b enters through the second end 520 and exits through the first end 510; or the first refrigerant flow path 143 a enters through the second end 520 and exits through the first end 510 and the second refrigerant flow path 143 b enters through the first end 510 and exits through the second end 520. The refrigerant in the first refrigerant flow path 143 a and the refrigerant in the second refrigerant flow path 143 b exchange heat through the plate heat exchanger or the double-pipe heat exchanger. Since the first refrigerant flow path 143 a and the second refrigerant flow path 143 b flow in opposite directions, the temperature difference between refrigerants in the first refrigerant flow path 143 a and the second refrigerant flow path 143 b is kept maximum, thus ensuring the heat exchange effect.

Regarding the refrigerant bridge 600, the refrigerant bridge 600 may be in various forms, as long as it enables, as the refrigerant passes through the first piping 140 (whether the refrigerant flows from the indoor heat exchanger to the outdoor side heat exchanger 141, or from the outdoor side heat exchanger 141 to the indoor heat exchanger), the refrigerant flow direction in the first refrigerant flow path 143 a to be always opposite to the refrigerant flow direction in the second refrigerant flow path 143 b so as to increase the temperature difference and thus ensure the heat exchange effect.

In this embodiment, by connecting the refrigerant inflow end of the first refrigerant flow path 143 a of the economizer 143 to the refrigerant bridge 600 and setting the flow direction of the second refrigerant flow path 143 b, the refrigerant flow directions in the first refrigerant flow path 143 a and the second refrigerant flow path 143 b are always opposite to each other (whether in the heating mode where the refrigerant flows from the indoor heat exchanger to the outdoor side heat exchanger 141, or in the cooling mode where the refrigerant flows from the outdoor side heat exchanger 141 to the indoor heat exchanger). In this way, the temperature difference between refrigerants in the first refrigerant flow path 143 a and the second refrigerant flow path 143 b is adequately maintained, so that the heat exchange effect between the first refrigerant flow path 143 a and the second refrigerant flow path 143 b can be ensured, which is conducive to ensuring the air replenishment effect of the economizer 143 on the compressor 110 in the heating mode, thus ensuring the heating capacity of the air conditioner in low-temperature environments; and which, at the same time, is conducive to ensuring the liquefaction effect (exhaust effect) of the economizer 143 on the refrigerant in the cooling mode, ensuring that the refrigerant entering the indoor throttle device is in the liquid state, thus eliminating the abnormal sound generated in the indoor throttling process.

It is worth noting that the conception of the present disclosure can be used not only for conventional air conditioners, but also for situations where multiple indoor heat exchangers are provided in the same one indoor unit 200, and also for situations where the refrigerant system has multiple indoor units 200. The increase in the complexity of the structure of a single indoor unit 200 itself, or the increase in the number of indoor units 200, will increase the length of the refrigerant pipeline and will make the effect of the present disclosure in eliminating abnormal sound more obvious.

The situation where multiple indoor heat exchangers are provided in a single indoor unit 200 will be described below:

The indoor unit 200 further includes a second heat exchanger 210, a second throttle regulator 230, and a thermal circulation device for delivering heat or cold from the indoor unit 200 into the room.

The air conditioner further includes a third piping 160 and a branch pipe 112 branching off from the discharge pipe 111, the third piping 160 connecting a first intersection point 211 of the first piping 140, the second throttle regulator 230, the second heat exchanger 210, and the branch pipe 112 in sequence so as to form a refrigerant circuit, where the first intersection point 211 is located between the first throttle regulator 240 and the outdoor side heat exchanger 141; and the economizer 143 is located at the first piping 140 between the first intersection point 211 and the outdoor side heat exchanger 141.

Here, in some embodiments, the thermal circulation device may be a wind wheel, and the rotation of the wind wheel delivers to the room the air for which heat has been exchanged with an initial heat exchanger and the second heat exchanger 210. Of course, in other embodiments, the thermal circulation device may also be a water circulation device, where the first heat exchanger 220 and the second heat exchanger 210 deliver heat or cold to the room through the circulating water flowing in the water circulation device.

On the basis of the above pipeline, the air conditioner can realize cooling by the first heat exchanger 220 and heating by the second heat exchanger 210, so that thermostatic dehumidification can be realized. Here, the first throttle regulator 240 includes a solenoid throttle valve, such as a solenoid expansion valve, and the second throttle regulator 230 includes a solenoid throttle valve, such as a solenoid expansion valve. The first switching device 131 is in the second state, where the first heat exchanger 220 performs cooling at which point the refrigerant is discharged from the discharge pipe 111 and enters the second heat exchanger 210 through the branch pipe 112 and the third piping 160; and the second heat exchanger 210 performs heating at which point the refrigerant flows out of the second heat exchanger 210 and then flows into the second piping 150 and, along the second piping 150, passes through the refrigerant bridge 600, the economizer 143, the outdoor side heat exchanger 141 and the suction pipe and flows back to the low-pressure suction port of the compressor 110.

In some other embodiments, the air conditioner further includes a second switching device 132, the second switching device 132 being capable of switching between a third switching state and a fourth switching state of the second switching device 132, where in the third switching state, the second switching device 132 causes the third piping 160 to communicate with the branch pipe 112, and in the fourth switching state, the second switching device 132 causes the third piping 160 to communicate with the suction pipe.

By the setting of the second switching device 132, in the third switching state, the air conditioner is in a thermostatic dehumidification state. In the fourth switching state, the air conditioner is in the cooling state, i.e., the first heat exchanger 220 and the second heat exchanger 210 perform cooling at the same time. The second switching device 132 may be a four-way valve. Also connected to the second switching device 132 is an auxiliary branch pipe, which communicates with the suction pipe when the third piping 160 communicates with the branch pipe 112. When the third piping 160 communicates with the low-pressure suction pipe 113, the auxiliary branch pipe communicates with the low-pressure suction pipe 113 and the branch pipe 112. A filter and a capillary are provided at the auxiliary branch pipe.

Of course, in some embodiments, the first switching device 131 and the second switching device 132 may exist at the same time, so that the air conditioner can be switched among three states of thermostatic dehumidification, heating only and cooling only.

In order to better regulate the subcooling degree of the outdoor side heat exchanger 141, the air conditioner further includes an outdoor side throttle regulator 142, the outdoor side throttle regulator 142 being located at the first piping 140 between the economizer 143 and the outdoor side heat exchanger 141. The outdoor side throttle regulator 142 includes an outdoor throttle valve, such as an electronic expansion valve.

The specific operation of the economizer 143 will be described below based on the situation where there exist a first indoor heat exchanger and a second indoor heat exchanger in the room.

In order to improve the heating capacity of the air conditioner at low temperatures, the air conditioner further includes the economizer 143; the economizer 143 is provided at the first piping 140 between the outdoor side heat exchanger 141 and the first intersection point 211, and the return pipe 146 of the economizer 143 communicates with the medium-pressure suction port of the compressor 110. The return pipe 146 may be in various forms, and the return pipe 146 may include only the return pipe 146 body, or may include the return pipe 146 body and the first communication pipe 148, one end of the first communication pipe 148 communicating with the return pipe 146 body and the other end communicating with the medium-pressure suction port of the compressor 110.

A first control valve 133 is provided at the return pipe 146 or on the first communication pipe 148 between the return pipe 146 and the medium-pressure suction port of the compressor 110. The compressor 110 at this point is an enhanced vapor injection compressor 110 having a low-pressure suction port and a medium-pressure suction port. The liquid pickup pipe 145 is provided with a liquid pickup throttle valve 144. In this way, the discharge from the compressor 110, after being switched by the first switching device 131 and the second switching device 132, enters the second heat exchanger 210 (the refrigerant enters through the third piping 160) and the first heat exchanger 220 (the refrigerant enters through the first piping 140), respectively, for heating, and the liquid refrigerant coming from the second heat exchanger 210 and the first heat exchanger 220 is divided into two parts when it passes through the economizer 143: the first part (through the refrigerant bridge 600 and the first refrigerant flow path 143 a) is directly subjected to throttling and pressure reduction by the outdoor side throttle regulator 142 (electronic expansion valve) and then enters the outdoor side heat exchanger 141 for evaporation and heat absorption; and the second part (through the second refrigerant flow path 143 b) is subjected to throttling and pressure reduction by the liquid pickup throttle valve 144 (electronic expansion valve), and then enters the economizer 143 through the liquid pickup pipe 145 for heat absorption and evaporation, and the evaporated medium-pressure saturated vapor passes through the return pipe 146, the first control valve 133, and the connection pipe and enters the medium-pressure suction port of the compressor 110, and is compressed after being mixed with the refrigerant from the low-pressure suction port of the compressor 110, thus solving the problems of low refrigerant flow, low back pressure, and high compression ratio in low-temperature environments, and improving the low-temperature heat production and the reliability of the system. With the technology of the present disclosure, when the outdoor environment temperature is low, the system design of the enhanced vapor injection compressor 110 and the economizer 143 increases the refrigerant suction amount of the compressor 110 in low-temperature environments, which in turn increases the heat production at a low temperature, while reducing the compression ratio in low-temperature environments, so the reliability of the system can be improved.

In order to improve the liquid pickup effect, the inflow end of the liquid pickup pipe 145 communicates with the first piping 140 between the economizer 143 and the outdoor side heat exchanger 141, while in some other embodiments, the inflow end of the liquid pickup pipe 145 may also communicate with the first piping 140 between the economizer 143 and the first intersection point 211 (in the absence of the first intersection point 211, the inflow end of the liquid pickup pipe 145 communicates with the first piping 140 between the economizer 143 and the first indoor throttle regulator). That is, the refrigerant flows in through the refrigerant outflow end of the economizer 143, which is conducive to improving the reliability of liquid pickup.

The junction between the inflow end of the liquid pickup pipe 145 and the first piping 140 is referred to as the liquid pickup point. As for the selection of the liquid pickup point, it will be beneficial for different working conditions to select corresponding liquid pickup points under different working conditions. When the inflow end of the liquid pickup pipe 145 communicates with the first piping 140 between the economizer 143 and the outdoor side heat exchanger 141, the connection position is referred to as a first liquid pickup point 134, or referred to as an upstream liquid pickup point; and when the inflow end of the liquid pickup pipe 145 communicates with the first piping 140 between the economizer 143 and the first intersection point 211 (or the first indoor throttle regulator), the connection position is referred to as a second liquid pickup point 135, or referred to as a downstream liquid pickup point. In the situation of heating by the indoor heat exchanger where the enhanced vapor injection needs to be turned on, the first liquid pickup point 134 or the upstream liquid pickup point is selected in order to replenish air to the compressor 110, thus increasing its heating capacity in low-temperature environments; and in the situation of cooling or thermostatic dehumidification (or dehumidification and reheating) by the indoor heat exchanger, the second liquid pickup point 135 or the downstream liquid pickup point is selected to cause the refrigerant entering the indoor unit 200 to be liquid as much as possible, thus avoiding the generation of abnormal sound during indoor throttling.

Referring to FIGS. 7-10, in some embodiments, in order to ensure the liquid pickup effect, the inflow end of the liquid pickup pipe 145 has a liquid pickup port 840 at a junction with the first piping 140, the liquid pickup port 840 being located below the first piping 140 around the liquid pickup port 840. By setting the position of the liquid pickup port 840 to be lower than that of the first piping 140, because the liquid refrigerant flows along the lower side pipe wall of the first piping 140 (the density of the refrigerant in the liquid state is greater than that in the gaseous state), so that when the refrigerant passes through the liquid pickup port 840, the liquid refrigerant enters preferentially under the action of gravity, thus ensuring that refrigerant picked up at the liquid pickup port 840 is in the liquid state.

The liquid pickup port 840 may be formed in many ways, such as, for example, providing a liquid pickup structure 800 at the junction of the liquid pickup pipe 145 with the first piping 140, where the liquid pickup structure 800 has a liquid pickup chamber 810 and three refrigerant ports that communicate with the liquid pickup chamber 810, namely, a first refrigerant port 830, a second refrigerant port 820 and a liquid pickup port 840, the liquid pickup port 840 being located below the first refrigerant port 830 and the second refrigerant port 820. Both the first refrigerant port 830 and the second refrigerant port 820 communicate with the first piping 140, and the liquid pickup port 840 communicates with the inflow end of the liquid pickup pipe 145. Specifically, the first refrigerant port 830 communicates with the first piping 140 near the outdoor heat exchanger, and the second refrigerant port 820 communicates with the first piping 140 near the first indoor throttle regulator. The liquid pickup port 840 is located at the bottom of the liquid pickup structure 800. The liquid pickup structure 800 may be in various shapes, such as rectangular, square, column, etc. The first refrigerant port 830 and the second refrigerant port 820 may be located at the two ends or at the top of the liquid pickup structure 800, but, of course, in some embodiments, the first piping 140 may also extend into the liquid pickup chamber 810 through the first refrigerant port 830 and the second refrigerant port 820.

In some other embodiments, in order to avoid unpleasant abnormal sound generated when the refrigerant in the gas-liquid two-phase state passes through the indoor throttle device, the air conditioner further includes a gas-liquid separator 120 and the economizer 143, the gas-liquid separator 120 being provided at the low-pressure suction pipe 113; and the economizer 143 is provided at the first piping 140 between the outdoor side heat exchanger 141 and the first intersection point 211, and the return pipe 146 of the economizer 143 communicates with the gas-liquid separator 120. The return pipe 146 may be in various forms, and the return pipe 146 may include only the return pipe 146 body, or may include the return pipe 146 body and the second communication pipe 147, one end of the second communication pipe 147 communicating with the return pipe 146 body and the other end communicating with the gas-liquid separator 120. For ease of control, in some examples, the return pipe 146 communicates with the gas-liquid separator 120 through the low-pressure suction pipe 113, and a second control valve 149 is provided at the return pipe 146 or the second connection pipe 250 between the return pipe 146 and the low-pressure suction pipe 113.

In the present disclosure, by adopting the system design with the economizer 143 on the basis of the three-pipe system, by controlling the liquid pickup throttle valve 144 (electronic expansion valve) in the system design circuit with the economizer 143, the refrigerant condensing temperature at the outlet of the outdoor side heat exchanger 141 is further reduced, which improves the subcooling degree and causes the refrigerant to condense completely to the liquid state, and the liquid refrigerant enters the indoor heat exchanger for heat absorption and evaporation after the throttling and pressure reduction by the indoor electronic expansion valves, so that the refrigerant passing through the indoor throttle devices is in the full liquid state, thus solving the problem of abnormal sound of refrigerant generated by the gas-liquid two-phase state refrigerant.

After the discharge of the compressor 110 is switched by the first switching device 131, the high-pressure and high-temperature gaseous refrigerant enters the outdoor side heat exchanger 141 for condensation and heat exchange, and the medium-temperature and high-pressure refrigerant in the gas-liquid two-phase state coming out of the outdoor side heat exchanger 141 enters the economizer 143 and is then divided into two parts: the first part, after the throttling and pressure reduction by the liquid pickup throttle valve 144, passes through the liquid pickup pipe 145 and then enters the economizer 143 for heat absorption and evaporation, and the evaporated gaseous refrigerant enters the gas-liquid separator 120 through the return pipe 146, the second control valve 149 (solenoid valve) and the connection pipe, and after being mixed with the gaseous refrigerant that has been subjected to heat absorption and evaporation by the indoor heat exchanger, enters the suction port of the compressor 110 together; and the second part, after further condensation and heat exchange by the economizer 143, is changed from gas-liquid two-phase refrigerant to pure liquid refrigerant, and this part of pure liquid refrigerant flows to the room, and then, after the throttling and pressure reduction by a dehumidification throttle valve and a reheating throttle valve, enters the first heat exchanger 220 and the second heat exchanger 210 for heat absorption and evaporation, respectively. Since the state of the refrigerant entering the first throttle regulator 240 and the second throttle regulator 230 (electronic expansion valve) changes from the gas-liquid two-phase state to the pure liquid state, the problem of abnormal sound of refrigerant caused by gas-liquid two-phase refrigerant when passing through throttle devices is solved.

In this embodiment, by means of the technical scheme of the present disclosure, the refrigerant condensing temperature at the outlet of the outdoor side heat exchanger 141 is further reduced, which improves the subcooling degree and causes the refrigerant to condense completely to the liquid state from the gas-liquid two-phase state, and the liquid refrigerant enters the indoor heat exchanger for heat absorption and evaporation after the throttling and pressure reduction by the indoor electronic expansion valves (the first throttle regulator 240 and the second throttle regulator 230), so that the refrigerant passing through the indoor throttle devices (the first throttle regulator 240 and the second throttle regulator 230) is in the full liquid state, thus solving the problem of abnormal sound of refrigerant generated by the gas-liquid two-phase refrigerant when passing through the throttle regulators, thereby improving the satisfaction of users

It is worth noting that, in some embodiments, the return pipe 146 communicates with the medium-pressure suction port of the compressor 110 and the gas-liquid separator 120, respectively, through different communication pipes, in which case the two communication pipes (the first communication pipe 148 and the second communication pipe 147) are provided with the first control valve 133 (near the compressor 110) and the second control valve 149 (near the gas-liquid separator 120), respectively. The return pipe 146 in this case includes the return pipe 146 body and the two communication pipes. In the heating mode, the second control valve 149 is closed and the first control valve 133 is opened, allowing the refrigerant to flow into the compressor 110 to improve heating capacity. In the cooling mode or thermostatic dehumidification mode, the first control valve 133 is closed and the second control valve 149 is opened to eliminate the abnormal sound. Of course, in some embodiments, the second control valve 149 may also be closed and the first control valve 133 opened due to special working conditions. By means of such settings, the air conditioner can adjust the first control valve 133 and the second control valve 149 according to the specific situation, thus improving the heating capacity of the air conditioner in the heating mode and reducing noise in the cooling and thermostatic dehumidification modes.

Regarding the specific connection of the compressor 110 to the economizer 143, the compressor 110 is an enhanced vapor injection compressor 110, and this compressor 110 has a medium-pressure suction port M (i.e., vapor injection port) in addition to the conventional high-pressure exhaust port P and low-pressure suction port S, where the medium-pressure refrigerant vapor enters the compressor 110 through this vapor injection port to increase the effective flow of refrigerant.

The a port of the economizer 143 is connected to a third port 630 of the refrigerant bridge 600, the b port of the economizer 143 is connected to a fourth port 640 of the refrigerant bridge 600, the c port of the economizer 143 is connected to the liquid pickup pipe 145, the d port of the economizer 143 is connected to the return pipe 146, the liquid pickup throttle valve 144 is connected in series to the liquid pickup pipe 145, the first control valve 133 is connected in series to a communication pipe, and the second control valve 149 is connected in series to another communication pipe, with one end of the communication pipe being connected to the medium-pressure suction port M of the compressor 110, and the other communication pipe being connected to the inlet end of the gas-liquid separator 120.

In some embodiments, the air conditioner further includes multiple indoor units 200, and the form of heat exchangers included in each indoor unit 200 may be different, for example, one or more of an indoor machine with thermostatic dehumidification function (having both the first heat exchanger 220 and the second heat exchanger 210), an ordinary cooling/heating indoor machine (having only one heat exchanger and a corresponding throttle device), and an indoor machine with a conversion device that can freely switch between cooling or heating states may be included, so that the air conditioner can perform mixed operations of thermostatic dehumidification, cooling and heating at the same time.

Specifically, the air conditioner further includes: a first connection pipe 260 branching off from a second intersection point 212 of the first piping 140 and a second connection pipe 250 branching off from the second piping 150, the second intersection point 212 being located between the first throttle regulator 240 and the outdoor side heat exchanger 141, and the air conditioner further includes multiple indoor units 200, the multiple indoor units 200 being connected in parallel to the first connection pipe 260 and the second connection pipe 250.

In some embodiments, in order to improve the reliability of the second switching device 132, instead of using a four-way valve, the second switching device 132 is controlled using two solenoid valves. Specifically, the third piping 160 communicates with the branch pipe 112 and communicates with the low-pressure suction pipe 113 or the second piping 150, with a third control valve 310 being provided at the branch pipe 112, and the third piping 160 communicates with the low-pressure suction pipe 113 or with the second piping 150 through the coupling pipe 114, with a fourth control valve 320 being provided at the coupling pipe 114. It is worth noting that the end of the coupling pipe 114 away from the third piping 160 may communicate with either the second piping 150 between the first switching device 131 and the indoor heat exchanger or the second piping 150 between the first switching device 131 and the gas-liquid separator 120. Since the third control valve 310 and the fourth control valve 320 are separate control valves, the structure is simpler and more stable and reliable compared to the four-way valve. In addition, the third control valve 310 and the fourth control valve 320 may be solenoid valves. The solenoid valve can still work stably and reliably when liquid refrigerant enters, while in the four-way valve, if liquid refrigerant enters, its working stability will be affected. Therefore, the use of separate third control valve 310 and fourth control valve 320 can improve the stability and reliability of the operation and state switching of the air conditioner.

It is worth noting that the states of the third control valve 310 and the fourth control valve 320 in the case of power off may be set according to the actual requirements of the working conditions. Take the third control valve 310 as an example. During the operation of the air conditioner, the third control valve 310 maintains a normally open state for a long period of time, in which case the third control valve 310 may be selected as a normally open valve, that is, most of its work can be completed in the power-off state, and it needs to be powered on only when the state of the third control valve 310 needs to be switched. Similarly, if the third control valve 310 maintains a normally closed state for a long time, it is selected to be a normally closed valve. In this way, it is conducive to reducing the electrical energy consumed by the second switching device 132 (including the third control valve 310) during the operation of the air conditioner, thus contributing to the rational use of energy.

In some embodiments, in order to simplify the pipeline structure, the third piping 160, the branch pipe 112 and the coupling pipe 114 are connected at the first junction Q. Of course, the low-pressure suction pipe 113 may communicate with the other two pipes through the coupling pipe 114. In this case, one three-way valve may be provided at the first junction Q instead of two two-way valves. The three-way valve realizes the communication of the third piping 160 to the coupling pipe 114 and the branch pipe 112, respectively, and may control the opening and closing of the coupling pipe 114 and the branch pipe 112, respectively. In this way, it is conducive to improving the convenience of the connection of the third piping 160, the coupling pipe 114 and the branch pipe 112.

Cooling Mode:

The high-temperature and high-pressure refrigerant is discharged from an exhaust pipe and passes through the first switching device 131, the first piping 140, the outdoor side heat exchanger 141, and the economizer 143 in sequence, and then enters an evaporation heat exchanger and the first heat exchanger 220, respectively, for cooling. One part flows out of the first heat exchanger 220, passes through the second piping 150 and the first switching device 131 (which may be absent in some embodiments), and flows into the gas-liquid separator 120; and the other part flows out of the evaporation heat exchanger, passes through the third piping 160 and enters the coupling pipe 114, and when the coupling pipe 114 communicates with the low-pressure suction pipe 113, the refrigerant enters the gas-liquid separator 120 through the low-pressure suction pipe 113; and when the coupling pipe 114 communicates with the second piping 150, the refrigerant flows into the second piping 150 through the coupling pipe 114, and then flows into the gas-liquid separator 120 through the second piping 150. In this process, the third control valve 310 is closed and the fourth control valve 320 is opened.

Heating Mode:

The high-temperature and high-pressure refrigerant is discharged from the exhaust pipe, and one part thereof passes through the first switching device 131 (which may be absent in some embodiments) and the second piping 150 in sequence, then enters the first heat exchanger 220 for heating, and then flows out of the first heat exchanger 220 and enters the first piping 140; and the other part passes through the branch pipe 112 and the third piping 160 in sequence and enters the second heat exchanger 210 for heating, and flows out of the second heat exchanger 210 and then enters the first piping 140, passes through the economizer 143, the outdoor side heat exchanger 141, and the first switching device 131, and then flows into the gas-liquid separator 120. In this process, the third control valve 310 is opened and the fourth control valve 320 is closed.

Thermostatic Dehumidification Mode:

The high-temperature and high-pressure refrigerant is discharged from the exhaust pipe, and one part thereof passes through the first switching device 131 (which may be absent in some embodiments), the first piping 140, the outdoor side heat exchanger 141, and the economizer 143 in sequence, and then enters the first heat exchanger 220 for cooling, and then passes through the second piping 150 and the first switching device 131 and flows into the gas-liquid separator 120. The other part passes through the branch pipe 112 and the third piping 160 in sequence and enters the second heat exchanger 210 for heating, and then flows into the first heat exchanger 220 for cooling. In this process, the third control valve 310 is opened and the fourth control valve 320 is closed.

The specifics of the refrigerant bridge 600 will be described with an example as follows:

The refrigerant bridge 600 has a first port 610, a second port 620, and a refrigerant passage that causes the first port 610 to communicate with the second port 620, and the refrigerant bridge 600 is connected in the first piping 140 through the first port 610 and the second port 620. Specifically, the first port 610 communicates with the first piping 140 near the outdoor side heat exchanger 141, and the second port 620 communicates with the first piping 140 near the indoor unit 200. The refrigerant bridge 600 further has a second port 620 and a fourth port 640, where the refrigerant bridge 600 is connected in the first refrigerant pipe of the economizer 143 through the second port 620 and the fourth port 640. The refrigerant may enter the refrigerant bridge 600 through the first port 610 or the second port 620, flow into the first refrigerant flow path 143 a through the third port 630 (the fourth port 640), pass through the first refrigerant flow path 143 a and then enter the refrigerant bridge 600 through the fourth port 640 (the third port 630), and then flow into the first piping 140 through the second port 620 or the first port 610.

There are many approaches of allowing unidirectional fluid flow between adjacent ports, as illustrated by two specific examples below:

In the first approach, the refrigerant bridge 600 has a third port 630 and a fourth port 640, with the two ends of the first refrigerant flow path 143 a being connected to the third port 630 and the fourth port 640, respectively; the first port 610 communicates with the third port 630 through a first bridge section 650, the first bridge section 650 allowing unidirectional fluid flow from the first port 610 to the third port 630; the third port 630 communicates with the second port 620 through a second bridge section 660, the second bridge section 660 allowing unidirectional fluid flow from the second port 620 to the third port 630; the second port 620 communicates with the fourth port 640 through a third bridge section 670, the third bridge section 670 allowing unidirectional fluid flow from the fourth port 640 to the second port 620; and the fourth port 640 communicates with the first port 610 through a fourth bridge section 680, the fourth bridge section 680 allowing unidirectional fluid flow from the fourth port 640 to the first port 610.

Two examples are given below for illustration:

Referring to FIG. 3, in the heating mode of the indoor machine, liquid pickup is conducted at the first liquid pickup point 134 (the upstream liquid pickup point):

The refrigerant, after flowing out of the indoor heat exchanger, enters the first piping 140, and enters the first bridge section 650 along the first piping 140 through the first port 610, flows out through the third port 630 and then enters the first refrigerant flow path 143 a of the economizer 143, enters through the first end 510 (in some embodiments, it may also enter through the second end 520 and flow out through the first end 510) into the plate heat exchanger or double-pipe heat exchanger for heat exchange and then flows out through the second end 520, and then enters the third bridge section 670 through the fourth port 640, flows out of the refrigerant bridge 600 through the second port 620 and enters the first piping 140, and then passes through the outdoor side throttle regulator 142 and the outdoor side heat exchanger 141 in sequence.

The refrigerant, after being subjected to liquid pickup at the first liquid pickup point 134 by the liquid pickup pipe 145, passes through the liquid pickup throttle valve 144 and enters through the second end 520 into the plate heat exchanger or double-pipe heat exchanger for heat exchange, and then flows out through the first end 510 (in some embodiments it may also enter through the first end 510 and flow out through the second end 520, as long as it is opposite to the first refrigerant flow path 143 a), and then enters the return pipe 146 and, along the return pipe 146, flows back to the medium-pressure suction port of the compressor 110.

Referring to FIG. 4, in the cooling or dehumidification and reheating mode of the indoor machine, liquid pickup is conducted at the second liquid pickup point 135 (the downstream liquid pickup point):

The refrigerant, after flowing out of the outdoor side heat exchanger 141, enters the first piping 140, and enters the second bridge section 660 along the first piping 140 through the second port 620, flows out through the third port 630 and then enters the first refrigerant flow path 143 a of the economizer 143, enters through the first end 510 (in some embodiments, it may also enter through the second end 520 and flow out through the first end 510) into the plate heat exchanger or double-pipe heat exchanger for heat exchange and then flows out through the second end 520, and then enters the fourth bridge section 680 through the fourth port 640, flows out of the refrigerant bridge 600 through the first port 610 and enters the first piping 140, and then enters the indoor heat exchanger.

The refrigerant, after being subjected to liquid pickup at the second liquid pickup point 135 by the liquid pickup pipe 145, passes through the liquid pickup throttle valve 144 and enters through the second end 520 into the plate heat exchanger or double-pipe heat exchanger for heat exchange, and then flows out through the first end 510 (in some embodiments it may also enter through the first end 510 and flow out through the second end 520, as long as it is opposite to the first refrigerant flow path 143 a), and then enters the return pipe 146, and along the return pipe 146 it flows back to the medium-pressure suction port of the compressor 110.

In the second approach, the refrigerant bridge 600 has a third port 630 and a fourth port 640, with the two ends of the first refrigerant flow path 143 a being connected to the third port 630 and the fourth port 640, respectively; the first port 610 communicates with the third port 630 through a first bridge section 650, the first bridge section 650 allowing unidirectional fluid flow from the third port 630 to the first port 610; the third port 630 communicates with the second port 620 through a second bridge section 660, the second bridge section 660 allowing unidirectional fluid flow from the third port 630 to the second port 620; the second port 620 communicates with the fourth port 640 through a third bridge section 670, the third bridge section 670 allowing unidirectional fluid flow from the second port 620 to the fourth port 640; and the fourth port 640 communicates with the first port 610 through a fourth bridge section 680, the fourth bridge section 680 allowing unidirectional fluid flow from the first port 610 to the fourth port 640.

Two examples are given below for illustration:

Referring to FIG. 5, in the heating mode of the indoor machine, liquid pickup is conducted at the first liquid pickup point 134 (the upstream liquid pickup point):

The refrigerant, after flowing out of the indoor heat exchanger, enters the first piping 140, and enters the fourth bridge section 680 along the first piping 140 through the first port 610, flows out through the fourth port 640 and then enters the first refrigerant flow path 143 a of the economizer 143, enters through the second end 520 (in some embodiments, it may also enter through the first end 510 and flow out through the second end 520) into the plate heat exchanger or double-pipe heat exchanger for heat exchange and then flows out through the first end 510, and then enters the second bridge section 660 through the third port 630, flows out of the refrigerant bridge 600 through the second port 620 and enters the first piping 140, and then passes through the outdoor side throttle regulator 142 and the outdoor side heat exchanger 141 in sequence.

The refrigerant, after being subjected to liquid pickup at the first liquid pickup point 134 by the liquid pickup pipe 145, passes through the liquid pickup throttle valve 144 and enters through the first end 510 into the plate heat exchanger or double-pipe heat exchanger for heat exchange, and then flows out through the second end 520 (in some embodiments it may also enter through the second end 520 and flow out through the first end 510, as long as it is opposite to the refrigerant flow direction in the first refrigerant flow path 143 a), and then enters the return pipe 146 and, along the return pipe 146, flows back to the medium-pressure suction port of the compressor 110.

Referring to FIG. 6, in the cooling or dehumidification and reheating mode of the indoor machine, liquid pickup is conducted at the second liquid pickup point 135 (the downstream liquid pickup point):

The refrigerant, after flowing out of the outdoor side heat exchanger 141, enters the first piping 140, and enters the third bridge section 670 along the first piping 140 through the second port 620, flows out through the fourth port 640 and then enters the first refrigerant flow path 143 a of the economizer 143, enters through the second end 520 (in some embodiments, it may also enter through the first end 510 and flow out through the second end 520) into the plate heat exchanger or double-pipe heat exchanger for heat exchange and then flows out through the first end 510, and then enters the first bridge section 650 through the third port 630, flows out of the refrigerant bridge 600 through the first port 610 and enters the first piping 140, and then enters the indoor heat exchanger.

The refrigerant, after being subjected to liquid pickup at the second liquid pickup point 135 by the liquid pickup pipe 145, passes through the liquid pickup throttle valve 144 and enters through the first end 510 into the plate heat exchanger or double-pipe heat exchanger for heat exchange, and then flows out through the second end 520 (in some embodiments it may also enter through the second end 520 and flow out through the first end 510, as long as it is opposite to the first refrigerant flow direction), and then enters the return pipe 146 and, along the return pipe 146, flows back to the medium-pressure suction port of the compressor 110.

Here, there are various approaches of allowing unidirectional fluid flow, taking the setting of one-way valve 690 as an example, the first bridge section 650, the second bridge section 660, the third bridge section 670, and the fourth bridge section 680 are each provided with a one-way valve 690 to achieve unidirectional fluid flow with each bridge section.

The above contents are only preferred embodiments of the present disclosure, and not to limit the scope of the present disclosure. Any equivalent structural transformation made under the inventive concept of the present disclosure using the specification and the accompanying drawings of the present disclosure, or directly/indirectly applied in other related technical fields are included in the scope of the present disclosure. 

1.-16. (canceled)
 17. An air conditioner comprising: an outdoor unit including a compressor and an outdoor heat exchanger; an indoor unit including a first heat exchanger and a first throttle regulator; a discharge pipe connected to a discharge side of the compressor; a low-pressure suction pipe connected to a low-pressure suction side of the compressor; a first piping connecting the discharge pipe, the outdoor heat exchanger, the first throttle regulator, and the first heat exchanger in sequence; a second piping connecting the first heat exchanger and the low-pressure suction pipe; an economizer arranged at the first piping between the outdoor heat exchanger and the first throttle device; a first refrigerant flow path arranged in the economizer and connected in the first piping through a refrigerant bridge; and a second refrigerant flow path arranged in the economizer, one end of the second refrigerant flow path communicating with the first piping through a liquid pickup pipe and another end of the second refrigerant flow path communicating with both a medium-pressure suction port of the compressor and the suction pipe through a return pipe; wherein: refrigerant flow directions in the first refrigerant flow path and the second refrigerant flow path are opposite to each other; and the outdoor unit further includes a first switching device configured to switch between: a first switching state, in which the first switching device causes the first piping to communicate with the suction pipe and causes the second piping to communicate with the discharge pipe; and a second switching state, in which the first switching device causes the first piping to communicate with the discharge pipe and causes the second piping to communicate with the suction pipe.
 18. The air conditioner of claim 17, wherein: the refrigerant bridge includes a first port, a second port, and a refrigerant passage that causes the first port to communicate with the second port; and the refrigerant bridge is connected in the first piping through the first port and the second port.
 19. The air conditioner of claim 18, wherein: the refrigerant bridge further includes a third port and a fourth port; two ends of the first refrigerant flow path are connected to the third port and the fourth port, respectively; the first port communicates with the third port through a first bridge section which allows unidirectional fluid flow from the first port to the third port; the third port communicates with the second port through a second bridge section which allows unidirectional fluid flow from the second port to the third port; the second port communicates with the fourth port through a third bridge section which allows unidirectional fluid flow from the fourth port to the second port; and the fourth port communicates with the first port through a fourth bridge section which allows unidirectional fluid flow from the fourth port to the first port.
 20. The air conditioner of claim 19, wherein the first bridge section, the second bridge section, the third bridge section, and the fourth bridge section are each provided with a one-way valve.
 21. The air conditioner of claim 18, wherein: the refrigerant bridge further includes a third port and a fourth port; two ends of the first refrigerant flow path are connected to the third port and the fourth port, respectively; the first port communicates with the third port through a first bridge section which allows unidirectional fluid flow from the third port to the first port; the third port communicates with the second port through a second bridge section which allows unidirectional fluid flow from the third port to the second port; the second port communicates with the fourth port through a third bridge section which allows unidirectional fluid flow from the second port to the fourth port; and the fourth port communicates with the first port through a fourth bridge section which allows unidirectional fluid flow from the first port to the fourth port.
 22. The air conditioner of claim 21, wherein the first bridge section, the second bridge section, the third bridge section, and the fourth bridge section are each provided with a one-way valve.
 23. The air conditioner of claim 17, wherein the liquid pickup pipe is provided with a liquid pickup throttle valve.
 24. The air conditioner of claim 17, wherein the return pipe includes: a return pipe body; a first communication pipe, one end of the first communication pipe communicating with the return pipe body and another end of the first communication pipe communicating with the medium-pressure suction port of the compressor, and the return pipe body or the first communication pipe being provided with a first control valve; and a second communication pipe, one end of the second communication pipe communicating with the return pipe body and another end of the second communication pipe communicating with the suction pipe, and the second communication pipe being provided with a second control valve.
 25. The air conditioner of claim 17, wherein an inflow end of the liquid pickup pipe communicates with the first piping at a location: between the economizer and the outdoor side heat exchanger; or between the economizer and the first throttle regulator.
 26. The air conditioner of claim 17, wherein an inflow end of the liquid pickup pipe has a liquid pickup port at a junction with the first piping, and the liquid pickup port is located below the first piping around the liquid pickup port.
 27. The air conditioner of claim 26, further comprising: a liquid pickup structure including: a liquid pickup chamber; a first refrigerant port communicating with the liquid pickup chamber; a second refrigerant port communicating with the liquid pickup chamber; and the liquid pickup port communicating with the liquid pickup chamber, the liquid pickup port being located below the first refrigerant port and the second refrigerant port.
 28. The air conditioner of claim 17, further comprising: a second heat exchanger; a second throttle regulator; a branch pipe branching off from the discharge pipe; and a third piping connecting an intersection point of the first piping, the second throttle regulator, the second heat exchanger, and the branch pipe in sequence; wherein: the intersection point is located between the first throttle regulator and the outdoor heat exchanger; and the economizer is located at the first piping between the intersection point and the outdoor heat exchanger.
 29. The air conditioner of claim 28, wherein: the third piping communicates with the branch pipe, and a third control valve is arranged at the branch pipe to control opening and closing of the branch pipe; and the third piping communicates with the low-pressure suction pipe or with the second piping through the coupling pipe, and a fourth control valve is arranged at the coupling pipe to control opening and closing of the coupling pipe.
 30. The air conditioner of claim 28, further comprising: a second switching device configured to switch between: a third switching state, in which the second switching device causes the third piping to communicate with the branch pipe, and a fourth switching state, in which the second switching device causes the third piping to communicate with the suction pipe.
 31. The air conditioner of claim 17, further comprising: an outdoor side throttle regulator located at the first piping between the economizer and the outdoor side heat exchanger.
 32. The air conditioner of claim 17, further comprising: a first connection pipe branching off from an intersection point of the first piping, the intersection point being located between the first throttle regulator and the outdoor heat exchanger; a second connection pipe branching off from the second piping; and wherein the indoor unit is one of a plurality of indoor units of the air conditioner that are connected in parallel to the first connection pipe and the second connection pipe.
 33. The air conditioner of claim 17, wherein the economizer includes a plate heat exchanger or a double-pipe heat exchanger having a first end and a second end opposite to each other.
 34. The air conditioner of claim 33, wherein: the first refrigerant flow path enters and exits the plate heat exchanger or the double-pipe heat exchanger through the first end and the second end, respectively; and the second refrigerant flow path enters and exits the plate heat exchanger or the double-pipe heat exchanger through the second end and the first end, respectively. 